How to check the SQL Statement Plan?

When you do an explain plan, then the appropriate DBMS_XPLAN api is
DBMS_XPLAN.DISPLAY.
When you do an actual execution - i.e. not with explain plan - then
DBMS_XPLAN.DISPLAY_CURSOR is the appropriate api.

Troubleshooting for DBMS_XPLAN.DISPLAY_CURSOR
Error:-
NOTE: cannot fetch plan for SQL_ID: 3pb80q4uks11n, CHILD_NUMBER: 0
Please verify value of SQL_ID and CHILD_NUMBER;
It could also be that the plan is no longer in cursor cache (check v$sql_p
lan)

grant select ON v_$session TO &&1;
grant select on v_$sql_plan to &&1;
grant select on v_$sql to &&1;

set serverouput off;